U.S. patent application number 10/810839 was filed with the patent office on 2004-09-16 for method for classifying and arranging metallic paint colors.
Invention is credited to Masuda, Yutaka, Tsukahara, Yukiyo.
Application Number | 20040179023 10/810839 |
Document ID | / |
Family ID | 12191959 |
Filed Date | 2004-09-16 |
United States Patent
Application |
20040179023 |
Kind Code |
A1 |
Masuda, Yutaka ; et
al. |
September 16, 2004 |
Method for classifying and arranging metallic paint colors
Abstract
Metallic paint colors are classified and arranged by determining
the representative color of any metallic paint color; calculating
the hue-tone value of said representative color; generating coating
color computer graphics indicating optical properties of said
metallic paint color in a prescribed range of angles of
observation; and preparing a coating color map by arranging said
coating color computer graphics over the hue-tone value of said
representative color in a hue-tone chart on the monitor screen of a
computer system.
Inventors: |
Masuda, Yutaka;
(Fujisawa-shi, JP) ; Tsukahara, Yukiyo;
(Hiratsuka-shi, JP) |
Correspondence
Address: |
WENDEROTH, LIND & PONACK, L.L.P.
2033 K STREET N. W.
SUITE 800
WASHINGTON
DC
20006-1021
US
|
Family ID: |
12191959 |
Appl. No.: |
10/810839 |
Filed: |
March 29, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10810839 |
Mar 29, 2004 |
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09236609 |
Jan 26, 1999 |
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6747662 |
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Current U.S.
Class: |
345/589 |
Current CPC
Class: |
G01J 3/52 20130101; G01J
3/46 20130101; G01J 3/504 20130101; G01J 3/50 20130101; G01J 3/462
20130101 |
Class at
Publication: |
345/589 |
International
Class: |
G09G 005/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 26, 1998 |
JP |
26,381/98 |
Claims
1. A method for determining the representative color of any
metallic paint color by a multiple regression formula of the
lightness and saturation of the metallic paint color at not fewer
than two angles of observation.
2. A method, as claimed in claim 1, for determining said
representative color of any metallic paint color as a hue-tone
value.
3. A method for classifying and arranging metallic paint colors,
comprising: determination of the representative one of the colors
of each metallic paint color; calculation of the hue-tone value of
said representative color; generation of coating color computer
graphics representing the optical properties of said metallic paint
color in a prescribed range of angles of observation; and
preparation of a coating color map by arranging said coating color
computer graphics over the hue-tone value of said representative
color in a hue-tone chart on the monitor screen of a computer
system.
4. A method, as claimed in claim 3, for determining the
representative color of any metallic paint color by a multiple
regression formula of the lightness and saturation of the metallic
paint color at not fewer than two angles of observation.
5. A method, as claimed in claim 3, for calculating the hue-tone
value of the representative color of any metallic paint color from
spectral reflectances under a condition of at least two angles
measured with a spectrophotometer.
6. A computer graphic apparatus comprising: a means to determine
said representative color of any metallic paint color out of
colorimetric values of said metallic paint color at a plurality of
angles of observation; a means to convert said representative color
into a hue-tone value; a means to generate coating color computer
graphics of said metallic paint color from the colorimetric values
of said metallic paint colors at a plurality of angles of
observation; and a means to arrange and display said coating color
computer graphics over the hue-tone value in a hue-tone chart
generated on a display unit.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a method for determining
the representative color of a metallic paint whose color varies
with the angle of observation, a method for classifying and
arranging metallic paint colors, and a computer graphic
apparatus.
[0003] The invention further relates to a computer graphic
apparatus for calculating the representative one of metallic paint
colors as a hue-tone value, arranging computer graphics of metallic
colors expressing their textures on a hue-tone chart, and thereby
displaying a chromatological classification of colors and their
textures at the same time.
[0004] The invention, since it permits identification of the
representative color of a paint which contains various effective
pigments such as aluminum flakes, mica flakes and plate iron oxide
in the coat and whose color varies with the angle of observation,
makes possible classification and arrangement of colors and
computerized search of colors. Furthermore, the invention provides
a computer-based design tool capable of simultaneously evaluating
color and texture by superposing computer graphics accompanied with
textures.
[0005] 2. Description of the Prior Art
[0006] The colors of the body coating of automobiles in recent
years are characterized by the dominance of metallic paints
containing various effective pigments (including aluminum flakes,
mica flakes and graphite). A metallic paint varies in color with
the angle of observation, gives metallic luster, pearly luster or
bicolor appearance (an effect to exhibit two or more colors
depending on the angle), and this feature is known as texture. As
techniques of chromatological classification of the body colors of
automobiles, the Munsell scale-and the hue-tone scale have been
extensively used for many years.
[0007] Solid coating colors can be classified according to a system
of color chips prepared with solid pigments. However, it is
difficult to extract the representative one out of various colors
which a metallic paint would manifest with changes in the angle of
observation. Reported methods for classification of others than
solid colors including ones for classifying angle-dependent colors
for the purpose of grading pearls (Japanese Laid-open [KOKAI]
Patent Publication No. 061635/81 and Japanese Laid-open [KOKAI]
Patent Publication No. 230778/86), but none of these methods is
applicable to so diverse colors as those of automobile body
coating.
[0008] For this reason, the conventional practice is for the
designer to look at metallic paint colors one by one against light,
observe color variation from highlight to shade by the eye and,
after imaging the representative one of the various colors in his
or her head, to finally determine the hue-tone value. This method,
however, involves the disadvantages of taking too long a time and
variance in results with the designer who appraises the color.
[0009] Furthermore, when the designer searches for a color he or
she images out of a tremendous variety of paint colors prepared in
the past, as the search takes so many man-hours per color checked
as the above-described procedure requires, the designer has no
other alternative than to make a rough guess to pick out the color
he or she remembers, and accordingly is substantially deterred from
retrieving the true color.
[0010] To sum up the problems noted above, the biggest point is how
to determine the representative color of a metallic paint whose
color varies with the angle of observation. In a calorimetric
approach, if an answer can be given to the question of the
calorimetric value taken in what angle can give the representative
value of that coating color, the value of that color can be figured
out in terms of HVC in the Munsell color scale or the commercial
available hue-tone scale, and a color whose value coincides with
this calculated value can be chosen as being approximately the
imaged color.
SUMMARY OF THE INVENTION
[0011] According to the present invention, in order to solve the
above-stated problems, there is provided a method by which the
representative color of any metallic paint color can be determined
by a multiple regression formula of the lightness and saturation of
the metallic paint color at not fewer than two angles of
observation.
[0012] According to the invention, in order to solve the
above-stated problems, there is provided a method for classifying
and arranging metallic paint colors, comprising:
[0013] determination of the representative one of the colors of
each metallic paint color;
[0014] calculation of the hue-tone value of said representative
color;
[0015] generation of coating color computer graphics representing
the optical properties of said metallic paint color in a prescribed
range of angles of observation; and
[0016] preparation of a coating color map by arranging said coating
color computer graphics over the hue-tone value of said
representative color in a hue-tone chart on the monitor screen of a
computer system.
[0017] According to the invention, in order to solve the
above-stated problems, there is provided a computer graphic
apparatus comprising:
[0018] a means to determine said representative color of any
metallic paint color out of colorimetric values of said metallic
paint color at a plurality of angles of observation;
[0019] a means to convert said representative color into a hue-tone
value;
[0020] a means to generate coating color computer graphics of said
metallic paint color from the colorimetric values of said metallic
paint color at a plurality of angles of observation; and
[0021] a means to arrange and display said coating color computer
graphics over the hue-tone value in a hue-tone chart generated on a
display unit.
[0022] The most important technique of the prevent invention is the
method to determine by calculation, when any metallic paint color
is given, the degree at which the measured value, out of those
values measured at many different angles, can give the
representative color of that metallic paint color. This core
technique is called the "algorithm to determine the representative
color of a metallic paint."
[0023] As a result of research through repeated experiments by eye
observation of metallic paint colors containing various effective
pigments as samples, the development of the "algorithm to determine
the representative color of a metallic paint" has been successfully
accomplished.
[0024] Thus, in architecting a computer system to retrieve a
designer-imaged color of a metallic paint which contains various
effective pigments and whose color varies in many ways with the
angle of observation, if the following three items are available,
the hue-tone value which is the imaged value can be calculated and,
by using this value, conversely any hue-tone value can be retrieved
from the reflection factors at many different angles measured in
the past:
[0025] a) a hard disk for storing the calorimetric values of a
metallic paint color at many different angles;
[0026] b) an "algorithm to determine the representative color of a
metallic paint" for calculating the angle of the representative
metallic color from those multi-angle data; and
[0027] c) an algorithm for calculating the representative color
into a hue-tone value.
[0028] By adding the following two more items, computer graphics
can be pasted on the calculated hue-tone value on the hue-tone
chart outputted on a computer graphic monitor screen, and totally
novel computer graphics permitting simultaneous appraisal of the
hue-tone value, which is a chromatological color class, and of
texture can be obtained:
[0029] d) computer graphics representing the metallic color
variation with each change in angle by the multi-angle reflection
factor; and
[0030] e) computer graphics of the hue-tone chart.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] FIG. 1 is a diagram showing the distribution of gloss with
the coat structure and angle variation of a metallic paint
color.
[0032] FIG. 2 is a diagram illustrating a computer graphic
apparatus according to a preferred-embodiment of the present
invention.
[0033] FIG. 3 is a diagram in which 32 metallic paint colors are
plotted on a hue-tone chart, with three-dimensional computer
graphics arranged over it.
MODE OF IMPLEMENTATION OF THE INVENTION
[0034] Determination of the representative color:
[0035] The algorithm to determine the representative color of a
metallic paint is as follows.
[0036] Generally, the distribution of gloss with the coat structure
and angle variation of a metallic paint color is as illustrated in
FIG. 1. There are scales of effective pigment (flakes of aluminum,
mica or the like) substantially in parallel to one another in a
color base containing a colored pigment or dye. The structure of
the metallic coat may as well be coating of a so-called color-clear
type, i.e. coating of a color-clear paint over a metallic base
containing no colored organic pigment.
[0037] The highlighted side, given a high reflection factor and
made lighter by the reflection of the effective pigment, manifests
the glitter of the effective pigment. The shaded side, where the
angle comes to a degree for the color of the pigment in the color
base to develop itself, is less bright than the highlighted
side.
[0038] On the other hand, whereas various hue-tone charts are
published today, this embodiment uses as its hue-tone chart a
laminate-coated version of M*M Chart II (hereinafter abbreviated to
M*MC) provided by Nippon Color & Design Research Institute,
which is extensively used for color designing of automobiles in
Japan. The reason for the choice of the laminate version of M*M
Chart II is that the laminate coat is close to the full gloss of
the top coat color of automobile bodies.
[0039] In this M*MC, as shown in FIG. 3, is a two-dimensional table
of which the horizontal axis is divided by a total of 44
graduations comprising 43 hues from 2.5R for red to 10RP for violet
and uncolored N (in 18 tones) and the vertical axis (Tone) is
divided by 25 graduations, wherein altogether 1,093 color chips
(43.times.25+18=1,093) are arranged.
[0040] With metallic paint colors used as samples, subjects who
were color designers engaged in the color design of the top coating
of automobiles, took part in a sensory test by eye observation, and
determined the representative color of each sample according to a
commercially available M*MC.
[0041] Next, in order to calculate the angle of observation this
representative color corresponds to, the metallic paint color was
actually measured at, for instance, five angles of observation with
a multi-angle spectrophotometer; the angle manifesting the smallest
color difference (JIS Z 8730) from the representative color was
figured out by using an equation, stated in the specification of
Japanese Laid-open [KOKAI] Patent Publication No. 10045/98, for
predicting the spectral reflectance of any angle; and this angle
was supposed to be the angle to give the representative color of
this metallic paint color sample. This angle is called the
representative angle D.
[0042] In practice, since the representative angle D of any given
metallic paint color should be predictively calculated from a
calorimetric value, an equation for predicting this angle was
searched for, and eventually it was discovered that the
representative angle D can be accurately calculated with the
function type of Equation (1).
D=a1.times.V1+a2.times.V2+b Equation (1)
[0043] Here, V1 represents a definition calculated from the
colorimetric value on the highlighted side. The highlighted side in
this context should be, with reference to FIG. 1, within the angle
range between 10 and 30 degrees, preferably between 22 and 28
degrees. The definition is a value calculated from a lightness L*
and a saturation c*, which are defined in JIS Z 8729, by Equation
(2).
V=squrt(L*{circumflex over ( )}2+c*{circumflex over ( )}2) Equation
(2)
[0044] V2 represents a definition calculated from the colorimetric
value on the shaded side. The shaded side should be within the
range between 35 and 55 degrees, more preferably between 40 and 50
degrees. Coefficients a1, a2 and b are multiple regression
coefficients, which can be easily obtained by multiple regression
analysis, wherein the object variable is the representative angle D
of the metallic paint color identified by eye observation, and the
explanatory variables are V1 and V2.
[0045] Thus, by determining a1, a2 and b in Equation (1) from
samples of a plurality of metallic paint colors, and V1 and V2 in
Equation (1) as stated above from the metallic paint color of which
the representative angle D is sought, D of this metallic paint
color is obtained.
[0046] The representative angle D was determined in this manner;
the reflection factor of that angle was determined by using the
equation, stated in the specification of Japanese Laid-open [KOKAI]
Patent Publication No. 10045/98, for predicting the spectral
reflectance of any angle; and the Lab* value of the representative
color was figured out by a method prescribed by JIS Z 8729.
[0047] Determination of the Hue-Tone Value:
[0048] Next, in order to convert the Lab* of the representative
color into a hue-tone value, the color differences between the Lab*
of the color chip of M*MC and the Lab* of the representative color
are calculated consecutively to find out the hue-tone value of a
color chip which gives the smallest color difference, and this was
supposed to be the hue-tone value of the representative one of
metallic paint colors.
[0049] Generation of the Coating Color Computer Graphics:
[0050] Coating color computer graphics of a metallic paint color is
the display of optical properties of the metallic paint color on
the monitor screen of a computer system, generated by using
computerized image processing techniques.
[0051] Coating color computer graphics shows, for instance as
illustrated in FIG. 1, optical properties in a range of observation
angles from 10 degrees (highlight) to 100 degrees (shade) in terms
of angle from regular reflection at an incident angle of 45
degrees, and for example as shown in FIG. 3, consists of the
rectangularly indicated part 6 in the hue-tone chart 5 on the
monitor screen of a computer system. In this rectangularly
indicated part 6, colors which are optical properties in a range of
observation angles from 10 degrees (highlight) to 100 degrees
(shade) are displayed from top to bottom. Preferably, the top part
of this rectangularly indicated part should be marked with the code
number of its metallic paint color.
[0052] This metallic paint color computer graphics can be generated
from spectral reflectances obtained by measurement with a
gonio-spectrophotometer, for instance, from 10 to 110 degrees in
one-degree graduations. Alternatively, this metallic paint color
computer graphics can as well be generated by determining the
spectral reflectance of the metallic paint color at a desired angle
from spectral reflectances measured under the five-angle condition
for the metallic paint color in accordance with what is indicated
in the specification of Japanese Laid-open [KOKAI] Patent
Publication No. 10045/98 and a regression formula and regression
coefficient calculated from the spectral reflectances measured
under the aforementioned five-angle condition.
[0053] Preparation of the Coating Color Map:
[0054] On a hue-tone chart prepared on the monitor screen of a
computer system, which may be, for example, an M*MC, the hue-tone
value of the representative color determined as described above is
plotted, and the coating color computer graphics generated as
described above is superposed over that plotted point.
[0055] The computer graphics obtained by the method so far
described is a new type of computer graphics permitting
simultaneous appraisal of the hue-tone value, which represents
chromatic and design-wise classifications, and the texture of the
metallic paint color, and can provide a design tool for coating
color development especially useful in the field of color designs
handling metallic paint colors.
[0056] Computer Graphic Apparatus:
[0057] Next will be described, with reference to FIG. 2, a computer
graphic apparatus according to a preferred embodiment of the
present invention.
[0058] This computer graphic apparatus, as illustrated in FIG. 2,
measures a metallic coat 1 with a portable spectrophotometer 2;
takes into a computer 3 reflection factors at many different angles
thereby obtained; figures out, by using Equations (1) and (2), the
angle that will give the representative color of any metallic
paint; figures out the reflection factor of that angle; converts it
into a Lab*; calculates the color difference from the already
measured color value Lab* of a color chip in the hue-tone chart;
calculates the hue-tone value of the representative color of the
metallic paint; and superposes the computer graphics of the
metallic paint color over the hue-tone chart on a monitor 4 of the
computer. By using this computer graphic apparatus, it is possible
to prepare, in a short period of time with an inexpensive and
compact apparatus, new graphics permitting simultaneous appraisal
of chromatic and design-wise classifications and the texture of the
metallic paint color.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0059] Determination of the Representative Color:
[0060] First will be described the procedure to determine the
representative color of a metallic paint.
[0061] Thirty-two metallic paint colors in a wide range of colors
and a wide range of textures containing metallic effective pigments
(including aluminum flakes, mica flakes, plate iron oxide, and
micro titanium oxide) were prepared as samples. Then, 17 color
designers and technicians involved in the use of colors and
coloring materials took part in an eye observation functional test
as subjects. They were asked to tell which hue-tone value in the
M*MC the representative color of each sample corresponded to and,
after totaling the answers, the average representative color chosen
by the 17 subjects was determined.
[0062] On the other hand, the measurement of colors was
accomplished with a portable gonio-spectrophotometer MA68, a
product of X-Rite of the United States. The spectral reflectances
of each of the 32 metallic paint color samples at five angles
against incidence at 45 degrees were obtained, including 15 and 25
degrees of specular component (the highlighted side), 45 degrees in
front, 75 and 110 degrees of the bottom color (shade).
[0063] Next, the reflection factor of the angle at which a color
closest to the representative color would be obtained was
determined by using the aforementioned equation, stated in the
specification of Japanese Laid-open [KOKAI] Patent Publication No.
10045/98, for predicting the spectral reflectance of any angle.
[0064] Then, multiple regression analysis was performed to apply
this angle to any metallic paint color, and Equation (3) was
obtained from the function type of Equation (1).
D=01.0612*V1+0.253*V2+15.11 Equation (3)
[0065] The multiple correlation coefficient of this multiple
regression formula proved as high as 0.8, and it was confirmed that
the angle giving the representative color of a metallic paint can
be estimated with high precision. With the measured values at 25
and 45 degrees used here for the definitions V1 and V2, the
lightness L* and the saturation c* were calculated by using JIS Z
8729.
[0066] Next, a random metallic color A1 was measured with the
spectrophotometer shown in FIG. 2, and the definitions V25 and V45
were calculated from the measured values at 25 and 45 degrees by
using Equation (2). Next, by using Equation (1), the representative
angle which would give the representative color of this metallic
paint was calculated.
[0067] Then, the reflection factor was calculated by using the
aforementioned equation, stated in the specification of Japanese
Laid-open [KOKAI] Patent Publication No. 10045/98, for predicting
the spectral reflectance of any angle, and the Lab* value was
obtained by using JIS Z 8729.
[0068] In this manner, the Lab* of the representative color A2 of
the random metallic color A1 was determined.
[0069] Determination of the Hue-Tone Value:
[0070] The Lab* values of 1,098 color chips of M*MC measured in
advance with a 45/0-degree spectrophotometer X968, a product of
X-Rite of the United States are stored into a storage unit of the
computer as the database.
[0071] Next, the color difference between the pertinent Lab* value
in the M*MC in the database and the Lab* value of the
representative color A2 determined as stated above was calculated
by the method of JIS Z 8730, and the hue-tone value of the M*MC
color chip giving the smallest color difference was supposed to be
the hue-tone value A3 of the representative color A2.
[0072] The representative colors of four metallic paint colors
according to eye observation and those based on the results of
calculation are listed in Table 1.
1TABLE 1 45/0-degree measured color Embodiment Example for
comparison values Eye-observed Answer of Calculated with no L* a*
b* color Equation (1) dM Judgment 45/0-degree L* dM Judgment no. 1
17.2 11.7 -32.3 7.5PB/DP2 7.5PB/Dp2 0.0 .circleincircle. 7.5PB/Dk2
2.0 .largecircle.- no. 2 61.3 -10.6 -4.3 7.5BG/LGR1 10BG/Lgr1 1.0
.largecircle. 7.5BG/Gr1 6.0 X no. 3 55.3 3.1 11.4 5YR/LGR1
7.5YR/Lgr2 1.4 .largecircle. 7.5YR/Gr1 6.1 X no. 4 46.8 -7.5 7.3
5G/LGR2 2.5G/Lgr2 1.0 .largecircle. 10GY/Gr2 6.3 X
[0073] In Table 1, from left to right, 1) no: the sample number; 2)
45/0-degree measured color L*a*b*: the L*a*b* value of measured
color at 45-degree incidence and 0-degree light reception; 3)
eye-observed color: the representative color of the metallic paint,
determined by an experiment of eye observation by six subjects,
this being the right answer, so to speak; 4) answer to Equation
(1); 5) dM: the distance between the eye-observed color (right
answer) on the hue-tone chart and the calculated color--the smaller
this value, the better, i.e. if it is 0, the hue-tone values of the
eye-observed color and of the calculated color will be identical;
6) judgment: {circle over (.smallcircle.)} denotes exact identity,
.largecircle., identity within the tolerance for eye observation,
and X, a large error; 7) example for comparison: the value
calculated by using the measured color of Lab* under the
45/0-degree condition, which is the colorimetric standard for
solids (the hue-tone value giving the smallest color
difference)--especially, light gray nos. 2 to 4 give dark values,
regarding which the judgment is X. In other words, if a 45/0-degree
colorimetric value is used as it is, the result will be a
considerably dark value because 45/0 degrees are close to the
shaded side. On the other hand, eye observation gave a result
somewhat toward the highlighted side. As a consequence, the
judgment was X as stated above.
[0074] As is evident from this Table 1, a fairly high level of
satisfaction was achieved.
[0075] Generation of the Coating Color Computer Graphics:
[0076] Coating color computer graphics was generated from spectral
reflectances obtained by measuring the aforementioned random
metallic paint color with a gonio-spectrophotometer, for instance,
from 10 to 110 degrees in one-degree graduations. This metallic
paint color computer graphics can as well be generated by
determining the spectral reflectance of the metallic paint color at
a desired angle from spectral reflectances measured under the
above-mentioned five-angle condition for the metallic paint color
in accordance with what is indicated in the specification of
Japanese Laid-open [KOKAI] Patent Publication No. 10045/98 and a
regression formula and regression coefficient calculated from the
spectral reflectances measured under the aforementioned five-angle
condition.
[0077] Preparation of the Coating Color Map:
[0078] On a hue-tone chart 5 prepared on the monitor screen of a
computer system, as shown in FIG. 3, the hue-tone value A3 of the
representative color A2 of the aforementioned random metallic paint
color A1, obtained as described above, was plotted, and the coating
color computer graphics generated as described above was superposed
over it.
[0079] In the same procedure as described above, the hue-tone value
of the representative color of other metallic paint colors were
plotted, and the coating color computer graphics for those metallic
paints were superposed over them.
[0080] In this way, by arranging computer graphics for a plurality
of metallic paint colors, the coating color map of metallic paint
colors shown in FIG. 3 was prepared.
* * * * *